---
title: "Insulation material guide"
url: https://bkgreenstone.com/reference/insulation-material-guide/
description: "Material classes described by what they are and where they normally suit. No brands, no products, and no performance figures, because those vary by specification rather."
---

# Insulation material guide

## All topics

- IN[Insulation & Air Sealing](https://bkgreenstone.com/topics/insulation-and-air-sealing/)
- WD[Windows & Doors](https://bkgreenstone.com/topics/windows-and-doors/)
- HV[Heating & Ventilation](https://bkgreenstone.com/topics/heating-and-ventilation/)
- PW[Plumbing & Water](https://bkgreenstone.com/topics/plumbing-and-water/)
- ME[Masonry & Exterior](https://bkgreenstone.com/topics/masonry-and-exterior/)
- MF[Millwork & Finishes](https://bkgreenstone.com/topics/millwork-and-finishes/)

## Reference sheets

- [Nominal lumber sizes](https://bkgreenstone.com/reference/nominal-lumber-sizes/)
- [Fastener and pilot sizes](https://bkgreenstone.com/reference/fastener-and-pilot-sizes/)
- [Insulation material guide](https://bkgreenstone.com/reference/insulation-material-guide/)

Material classes described by what they are and where they normally suit. No brands, no products, and no performance figures, because those vary by specification rather than by class.

*Material classes by form, usual position and limiting factor. Units: no units - descriptive.*

| Material class | Usual form | Normally used at | Limiting factor |
|---|---|---|---|
| Mineral fibre batt | Semi-rigid batt or roll | Between joists, studs and rafters | Needs a friction fit; performance falls off sharply with gaps |
| Loose fill | Blown or poured granules or fibre | Open horizontal roof spaces | Settles and cannot be used on a slope |
| Rigid foam board | Faced or unfaced boards | Continuous layers over or under structure | Joints must be sealed; unforgiving of an uneven substrate |
| Wood fibre board | Rigid or flexible board | Vapour-open internal and roof build-ups | Thicker for the same reduction; must be able to dry |
| Sheep wool and other natural fibre | Batt or roll | Between timbers where vapour openness matters | Handles moisture well but needs protection from pests |
| Blown cellulose | Dense-packed fibre | Closed cavities and stud bays | Requires the cavity to be genuinely closed and access holes made good |
| Reflective multifoil | Thin layered foil | Where an adjacent air gap can be guaranteed | Depends entirely on a maintained air gap and a clean surface |

Scroll the table sideways for the remaining columns.

## Notes on using this sheet

- Class describes form and behaviour, not a specification. Two products in the same class can differ substantially.
- Any class installed with gaps performs closer to no insulation than to its intended value, which is why fit matters more than class in most retrofits.
- Whether an assembly can dry is a property of the whole build-up, not of the insulation alone.

[Back to all reference sheets](https://bkgreenstone.com/reference/)